1. Description of the Prior Art
It is well known in the prior art to remove second harmonic signals generated in a power amplifier resonant transmission line, also referred to as a tank circuit or tank cavity. However, the prior art has removed this undesirable signal in a manner quite different from the teachings of the present invention. Typically, the prior art has utilized the principal of trapping the second harmonic by the use of a second harmonic stub in the RF output line. In addition, such prior art arrangements have utilized low pass filters to further remove second and higher harmonics.
In particular, a typical prior art device may utilize a transmission line stub having a variable short which is adjustable to attenuate the second harmonic. This adjustment is needed to accommodate the selection of the fundamental by tuning within the tank circuit. Such an arrangement is more costly and results in a lower power amplifier efficiency than the present invention.
2. Field of the Invention
The field of art to which this invention pertains is power amplifier tank cavities for generating an RF signal for transmitters and in particular to means for not attenuating but removing the second harmonic of the fundamental generated in such cavities in a manner which maximizes the efficiency of the system.